cilium: IPV6 access to node is lost after installing cilium with ipv6 enabled

Bug report

General Information

• Cilium version (run cilium version) Client: 1.9.1 975b66772 2020-12-04T18:16:09+01:00 go version go1.15.5 linux/amd64 Daemon: 1.9.1 975b66772 2020-12-04T18:16:09+01:00 go version go1.15.5 linux/amd64
• Kernel version (run uname -a) Linux srv-oajxq 5.4.0-54-generic #60-Ubuntu SMP Fri Nov 6 10:37:59 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
• Orchestration system version in use (e.g. kubectl version, Mesos, …) Client Version: version.Info{Major:“1”, Minor:“20”, GitVersion:“v1.20.1”, GitCommit:“c4d752765b3bbac2237bf87cf0b1c2e307844666”, GitTreeState:“clean”, BuildDate:“2020-12-18T12:09:25Z”, GoVersion:“go1.15.5”, Compiler:“gc”, Platform:“linux/amd64”} Server Version: version.Info{Major:“1”, Minor:“20”, GitVersion:“v1.20.1”, GitCommit:“c4d752765b3bbac2237bf87cf0b1c2e307844666”, GitTreeState:“clean”, BuildDate:“2020-12-18T12:00:47Z”, GoVersion:“go1.15.5”, Compiler:“gc”, Platform:“linux/amd64”}

How to reproduce the issue

cilium is installed on a k8s kubeadm installed server that obtains its IPv6 address and prefix via SLAAC on ens3

cilium is installed via Helm.

The result is that both ens3 and cilium_host end up with different IPv4 addresses but the same IPv6 address.

$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq state UP group default qlen 1000
    link/ether 02:24:19:f1:d2:2a brd ff:ff:ff:ff:ff:ff
    inet 10.241.210.42/30 brd 10.241.210.43 scope global dynamic ens3
       valid_lft 2473sec preferred_lft 2473sec
    inet6 2a02:1348:17c:748a:24:19ff:fef1:d22a/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 3481sec preferred_lft 3481sec
    inet6 fe80::24:19ff:fef1:d22a/64 scope link 
       valid_lft forever preferred_lft forever
3: cilium_net@cilium_host: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether ea:43:1a:66:ba:0c brd ff:ff:ff:ff:ff:ff
    inet6 fe80::e843:1aff:fe66:ba0c/64 scope link 
       valid_lft forever preferred_lft forever
4: cilium_host@cilium_net: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 82:63:9b:3f:b9:20 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.159/32 scope link cilium_host
       valid_lft forever preferred_lft forever
    inet6 2a02:1348:17c:748a:24:19ff:fef1:d22a/128 scope global 
       valid_lft forever preferred_lft forever
    inet6 fe80::8063:9bff:fe3f:b920/64 scope link 
       valid_lft forever preferred_lft forever
5: cilium_vxlan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether b2:61:4b:c1:e4:61 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::b061:4bff:fec1:e461/64 scope link 
       valid_lft forever preferred_lft forever
7: lxc_health@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 36:09:4a:e2:b3:1d brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::3409:4aff:fee2:b31d/64 scope link 
       valid_lft forever preferred_lft forever
11: lxc1f951ae922b5@if10: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 42:02:d8:fc:b3:7d brd ff:ff:ff:ff:ff:ff link-netns cni-5c5b4a35-015c-b4e7-8cf0-65094143a9cf
    inet6 fe80::4002:d8ff:fefc:b37d/64 scope link 
       valid_lft forever preferred_lft forever
15: lxc02ded1934caa@if14: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 3e:9f:73:d2:b4:13 brd ff:ff:ff:ff:ff:ff link-netns cni-a7b32eab-3909-902f-3e02-cca756dbc5a8
    inet6 fe80::3c9f:73ff:fed2:b413/64 scope link 
       valid_lft forever preferred_lft forever
17: lxceaca9073e91d@if16: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 22:e4:12:48:59:5e brd ff:ff:ff:ff:ff:ff link-netns cni-f0123261-5a17-ba81-5964-058a1fc742a8
    inet6 fe80::20e4:12ff:fe48:595e/64 scope link 
       valid_lft forever preferred_lft forever